Thousands and thousands of people stranded after the computers at american airlines went down tuesday. They are back up this morning. But more cancellations are expected. Abc's david kerley is at reagan national airport with the very latest this morning. Good morning to you, david. Reporter: Good morning, josh. There are a lot of flyers waking up in places they do not want to be. They are grounded. Not by weather, but technology. The third largest airline still k on schedule this morning after a massive computer crash left thousands of passengers stranded. Systems are down. I tried to check in online. The app isn't working. Very frustrating. Upsetting. Not happy at all. Reporter: The crash in computer system meant every ticket agent, gate agent saw their screens go dark. The same at the airline's operation center. No way to track bags, update schedules or flight plans. American had no choice. It stopped everything, grounding every plane. They were parked in chicago, miami and dallas. There's nothing you can do. You just have to stand in line and hope you can get on your flight. Reporter: They started cascadbefore the day was over. Nearly 78800 flights never happened. Embarrassed the ceo took to youtube to explain. Unfortunately, in this case we had a software issue that impacted both our primary and backup systems. Reporter: So all the airline could do was apologize and start shelling out cash for refunds or to pay any additional cost to book passengers on other airlines so they could finally get to where they wanted to go. I was just inside. There are long lines in washington. I'm sure at other airports as flyers trying to get where they want to go today. If yesterday was a migraine today will be a headache. American admits, josh, they will have to cancel more flights today. Just a reminder how much we rely on technology. Indeed, it is.

This transcript has been automatically generated and may not be 100% accurate.

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